There is a lot of half truth floating about when it comes to the diesel engines avalble for the DA42.
Both the engines are based on Merc car engines with Thielert favoring the alloy crackcase and Austro going for the steel, the Thielert is lighter but the Austro produces more power, in realistic terms the performance delivered to the aircraft is much the same. Austro have been very conservative with the rated power and I am told that in the test cell the Austro has run as for a long time at power settings of up to 200bhp.
The Austro has the advantage of using the experience of Thielert in the development, the biggest problem that was encountered with the Thielert was corrosion in the cylinder heads, Thielert had no problems with this in the aircraft that they retrofitted or with the Robin instalation that they had total control over. The corrosion was found to be an electrolytic reaction between the cylinder head and the heat exchangers with the coolant forming the electrolyte. Who wrote the spec for the heat exchangers is unclear but following the problem Astro have been very carefull to mandate the approved coolant.
Thielert now have a lot of running time on the engines in UAV's and the engine is starting to mature, I am not sure what other products the Austro is used in but I would think that Austro will have a long way to go to match Thielerts flight time.
The Austro was an engine born out of the difficultys between the two company's and it is interesting to see how two engines based on a very similar car engine have evolved, I do however feel that Austro have taken advantage of a lot of hard won development at Thielert.